This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. This translational research project is prompted by the need to develop new evaluative tools to assess the preclinical safety of tissue engineered biological heart valves intended for use in infants, children and young adults. Chronic in vivo studies in sheep may not be sufficient to adequately evaluate primate-specific complex biology, immune and inflammatory-mediated responses that are critical factors expected to significantly impact the safety, performance and therapeutic durability of a tissue engineered biological heart valve for human clinical use. Such a tissue engineered cardiovascular construct, by definition, includes both cells (derived from the patient/recipient), and structural proteins (derived from the donor heart valve). The putative prototypical tissue engineered pulmonary valved conduit scaffold to be tested consists of either an allograft (homograft;ie, baboon species for orthotopic transplant) or a xenograft (human semilunar valve) scaffold. Both test valve types will have been engineered to effect removal of donor cells and reduce antigenicity (using our novel decellularization process). This design will test the safety of the acellular construct and the immunogenic and proinflammatory potential of allograft (papio) versus xenograft (human) structural proteins.